Hi Anonymous,
According to MBB internal rules, no interview coaching of candidates is allowed (both commercial and non-commercial activities), apart from the official mentoring scheme that firms provide.
However, you can try to develop your network and reach out to some consultants on an informal way - might not be allowed officially, but I know that some people do it nevertheless (definitely not recommended from consultant's side - rules are strict and enforced - but that's not of your primary concern at the moment).
Hope that helps - if so, please be so kind and give it a thumbs-up with the green upvote button below!
Robert